FAILURE MAP
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FA-26621 / HTTP ranges / Open access

Range stream idle deadlines advance only on actual byte progress · case 01

Range stream idle deadlines advance only on actual byte progress.

Verified by executionVariant 1 · 6 checks per implementationDownload source bundle ↓JSON ↗

ROOT CAUSE

The stream-timeout-last-progress decision uses return now+timeout.

VERIFIED REPAIR

Apply the bounded decision exactly: return (now if delivered>0 else last)+timeout

Unsuccessful approach: The partial repair uses return last+timeout, which still violates the stated contract.

Case contract

Return next idle deadline; positive delivered resets progress to now, zero-byte activity retains last. All integers nonnegative.

Why this case matters

Range responses combine representation identity, conditional requests, framing, and partial-object state.

1 / The failure

Exit 1
"""Failure Map reference implementation. Python standard library only."""
import json

N = 1
observations = []
def solve(last, now, delivered, timeout):
    return now+timeout
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('stream-timeout-last-progress fixture 0', solve(N,3*N,0,N), 2*N)
check('stream-timeout-last-progress fixture 1', solve(N,3*N,N,N), 4*N)
check('stream-timeout-last-progress fixture 2', solve(0,0,0,N), N)
check('stream-timeout-last-progress fixture 3', solve(0,N,1,0), N)
check('stream-timeout-last-progress fixture 4', solve(N,N,0,N), 2*N)
check('stream-timeout-last-progress fixture 5', solve(0,N,0,0), 0)
print(json.dumps({"observations": observations, "passed": all(x["passed"] for x in observations)}, ensure_ascii=False))
raise SystemExit(0 if all(x["passed"] for x in observations) else 1)
Boundary fixtureActualExpectedOutcome
stream-timeout-last-progress fixture 042Failed
stream-timeout-last-progress fixture 144Passed
stream-timeout-last-progress fixture 211Passed
stream-timeout-last-progress fixture 311Passed
stream-timeout-last-progress fixture 422Passed
stream-timeout-last-progress fixture 510Failed

SHA-256 / 41ea829187437c11bfc9f43fd43323d0edf0ea849f314c471570207fa7dc87dd

2 / The unsuccessful fix

Exit 1
"""Failure Map reference implementation. Python standard library only."""
import json

N = 1
observations = []
def solve(last, now, delivered, timeout):
    return last+timeout
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('stream-timeout-last-progress fixture 0', solve(N,3*N,0,N), 2*N)
check('stream-timeout-last-progress fixture 1', solve(N,3*N,N,N), 4*N)
check('stream-timeout-last-progress fixture 2', solve(0,0,0,N), N)
check('stream-timeout-last-progress fixture 3', solve(0,N,1,0), N)
check('stream-timeout-last-progress fixture 4', solve(N,N,0,N), 2*N)
check('stream-timeout-last-progress fixture 5', solve(0,N,0,0), 0)
print(json.dumps({"observations": observations, "passed": all(x["passed"] for x in observations)}, ensure_ascii=False))
raise SystemExit(0 if all(x["passed"] for x in observations) else 1)
Boundary fixtureActualExpectedOutcome
stream-timeout-last-progress fixture 022Passed
stream-timeout-last-progress fixture 124Failed
stream-timeout-last-progress fixture 211Passed
stream-timeout-last-progress fixture 301Failed
stream-timeout-last-progress fixture 422Passed
stream-timeout-last-progress fixture 500Passed

SHA-256 / 50eed375f718535e7b74ded7e3b4126ae2be13000bef92c083206a523ca2cbb2

3 / The verified repair

Exit 0
"""Failure Map reference implementation. Python standard library only."""
import json

N = 1
observations = []
def solve(last, now, delivered, timeout):
    return (now if delivered>0 else last)+timeout
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('stream-timeout-last-progress fixture 0', solve(N,3*N,0,N), 2*N)
check('stream-timeout-last-progress fixture 1', solve(N,3*N,N,N), 4*N)
check('stream-timeout-last-progress fixture 2', solve(0,0,0,N), N)
check('stream-timeout-last-progress fixture 3', solve(0,N,1,0), N)
check('stream-timeout-last-progress fixture 4', solve(N,N,0,N), 2*N)
check('stream-timeout-last-progress fixture 5', solve(0,N,0,0), 0)
print(json.dumps({"observations": observations, "passed": all(x["passed"] for x in observations)}, ensure_ascii=False))
raise SystemExit(0 if all(x["passed"] for x in observations) else 1)
Boundary fixtureActualExpectedOutcome
stream-timeout-last-progress fixture 022Passed
stream-timeout-last-progress fixture 144Passed
stream-timeout-last-progress fixture 211Passed
stream-timeout-last-progress fixture 311Passed
stream-timeout-last-progress fixture 422Passed
stream-timeout-last-progress fixture 500Passed

SHA-256 / a17048bb3235c1fc68305b8ff902b0468b668afdab90a43a42b10985a4e4c457

Verification & scope

Deterministic simplified range service, with stipulated local policies and already parsed trusted inputs; not a complete HTTP implementation. This reproducer isolates one failure mechanism. Results cover the supplied fixtures. Variants within a family share a test contract and should remain grouped when constructing evaluation splits. Related mechanisms with a shared evaluation_group must also remain together; these controlled models are not independent production incidents.

Observations recorded using Python 3.12.14 at 2026-09-29T14:41:17.575351+00:00.

Case digest / 17647e780e03ad090e4ef9874c4b679a841627a69f5e058966d5ce06a2deb884